Electrochemical cells, such as electrolytic cell stacks used in advanced electrolytic oxygen generators in submarines, space craft, etc., are commonly used to convert water into diatomic hydrogen and oxygen gas. It is critical in such generators to maintain pressure differentials within a very limited range within the cells themselves. Modern electrolytic cells and/or cell stacks operate at increasingly higher total operating flow rates and/or pressures to achieve optimal performance. Additionally, modification of traditionally submarine-based electrolytic cell stacks for efficient use in space craft requires that overall weights and volumes of the cell stacks be reduced as much as possible.
In use of such a cell stack for generation of oxygen and hydrogen gas, the rates of production of oxygen and hydrogen gas relative to each other are typically constant. However, because those product gases are compressible, their operating pressures within the cells and/or cell stack are a function of use of each gas downstream of the stack, and the relative use of each gas is variable. For example in a submarine or space craft, there may be a sudden and critical demand for an increased usage of oxygen gas, while the requirement for hydrogen gas remains constant. Consequently, operating pressures of the oxygen may suddenly decrease upstream of the demand, within the cell stack, thereby increasing the pressure differential across the cells of the stack. Additionally, such a cell stack is capable of catastrophic failure if a pressure differential is sufficient to cause a breach in ordinary barriers within the cells between the product gases. Under ordinary high operating pressures of modern electrolytic cell stacks, mixing of hydrogen and oxygen gas as a result of such a failure could easily be at the stoichiometric quantities required to produce an explosion. Moreover, even at pressure differentials far less than that which can cause a breach, excess pressure differentials as low as a few inches of water can force an electrolyte (such as a potassium hydroxide--water solution) through a cell membrane causing the electrolyte to flow out of the cell into gas product distribution lines, requiring shutdown for clean up and/or repair.
Consequently it is critical to maintain the pressure differential of the product gases in an electrolytic cell and/or cell stack within a very narrow acceptable range. Current systems for regulating pressure differentials within such cell stacks have relied upon an electronic system demand regulator that controls the output of a first side of the cell stack (e.g., the oxygen side), while the output of a second side (e.g., the hydrogen side) is controlled by a standard delta-p regulator that references the flow rate of the first side. Additionally, in the event the system demand and delta-p regulators allow an excess pressure differential beyond an acceptable range, modern electrolytic cell stack systems use separate accumulator tanks for each side to immediately compensate for such an excess pressure differential. The accumulator tanks inject into the side experiencing a lower relative pressure an adequate amount of gas to return the pressure differential to within the acceptable range.
Use of the system control regulator, delta-p regulator, accumulator volume tanks, and the standard piping and valve hardware, and switch mechanisms that operate such current systems for regulating pressures within modern electrolytic cell stacks adds enormous weight, volume, risk and cost factors to efficient operation of modern electrolytic cells and/or cell stacks.
Additionally, there are many pressure differential regulators for more conventional, non-electrolytic cell fluid delivery systems that control pressure differentials between differing fluids within such conventional systems. For example, in large hotels having a plurality of shower heads that mix hot and cold water for personal bathing, a sudden drop in the flow rate of the cold water must be immediately compensated for by a commensurate drop in the flow rate of the hot water to avoid scalding a user of the shower. Similarly, beverage dispenser heads that mix syrup, water and carbon dioxide gas under pressure, must mix the gas with the syrup and water at a constant pressure, while the pressure of the gas as delivered from a storage tank is constantly declining.
Known pressure differential regulators for these conventional systems maintain the pressure differential of differing fluids in such systems within a specific range through use of a single pressure sensing diaphragm positioned between two separate pressure sensing chambers. Two separate valves are placed on opposed sides of the diaphragm so that a separate valve controls flow through each chamber. Such regulators work by structuring the relationship between each valve and the pressure sensing diaphragm so that an increase in relative pressure within a first chamber results in a simultaneous decrease in flow rate out of that first chamber and an increase in flow rate out of the second chamber.
U.S. Pat. No. 3,688,790 to Esten for a "Pressure Balance Valve" shows a typical regulator for a multiple shower head environment, wherein the relationship between the pressure sensing diaphragm, two chambers and two valves is disclosed. As shown in the Esten Patent, when the pressure of a fluid in a first chamber increases relative to the pressure of a fluid in the second chamber, the diaphragm expands into and contracts the internal volume of the second chamber, thereby causing a first valve affixed to a first side of the diaphragm and projecting into the first chamber to adjust to restrict flow out of the first chamber, while simultaneously causing a second valve affixed to an opposed second side of the diaphragm and projecting into the second chamber to adjust to increase flow out of the second chamber.
For example, in a regulator such as the "balance valve" shown in the Esten Patent, cold water may flow through a first chamber and hot water may flow through a second chamber and, after leaving the regulator, the cold and hot water are next mixed together downstream of the regulator and then discharged through a shower head. If a sudden drop in pressure or flow rate of cold water into the first chamber occured as a result of a demand for cold water upstream of the regulator (e.g., via toilet flushing, etc.), the diaphragm would sense the change in relative pressures between the first and second chambers and expand into the first chamber and away from the second chamber to enhance flow of cold water out of the first chamber, while simultaneously restricting flow of hot water out of the second chamber. Because the valves within sensing chambers of conventional pressure differential regulators act to enhance outflow of fluids out of their sensing chambers upon contraction of the sensing chambers, it is appropriate to refer to such valves as contracted sensing chamber outflow enhancement valves, as will be done hereinbelow.
As is readily apparent, such conventional pressure differential regulators are structured to control pressure differentials between differing fluids downstream of the regulators as a result of fluctuations of pressures and/or flow rates upstream of the regulators. Therefore, positioning such regulators downstream of the cell stacks would have the effect of increasing pressure differentials within the cell stack upon a sudden downstream decrease in pressure in one side of the regulator output. Moreover, because source materials for electrolytic cells and/or cell stacks are typically liquid and product materials are differing gases, positioning conventional pressure differential regulators upstream of the cell stacks, in the flow of the liquid phase of the source materials, cannot effect pressure differentials within the cell stack, or in individual cells. Consequently, conventional pressure differential regulators are not capable of controlling pressure differentials within an electrolytic cell or electrolytic cell stack.
Accordingly, it is the general object of the present invention to provide an improved pressure differential regulator that overcomes problems of the prior art.
It is a more specific object to provide an improved pressure differential regulator that overcomes excess weight, volume, risk and cost problems of known systems for regulating pressure differentials in electrolytic cells and/or cell stacks.
It is another specific object to provide an improved pressure differential regulator for controlling pressure differentials between differing product fluids within an electrolytic cell and/or cell stack that minimizes the risk of the differing product fluids of the cell and/or cell stack mixing with each other.
It is another object to provide an improved pressure differential regulator for controlling pressure differentials between differing fluids upstream of the regulator in response to demands for the fluids downstream of the regulator.
It is yet another object to provide an improved pressure differential regulator for electrolytic cells and/or cell stacks that may be economically encased within a single housing.
The above and other advantages of this invention will become more readily apparent when the following description is read with the accompanying drawings.